r - 如何按组计算相关性

Question

我正在尝试运行迭代 for 循环来计算因子变量级别的相关性。我的数据集中有 32 个团队的每个团队的 16 行数据。我想将年份与每个团队的积分相关联。我可以一一完成，但希望在循环方面做得更好。

correlate <- data %>%
  select(Team, Year, Points_Game) %>% 
  filter(Team == "ARI") %>% 
  select(Year, Points_Game)

cor(correlate)
我通过以下方式制作了一个对象“团队”:

teams <- levels(data$Team)

使用 [i] 遍历所有 32 个团队以获得每个团队的年份和积分相关性的一些帮助将非常有帮助!

Answer 1

require(dplyr)

# dummy data
data = data.frame(
  Team = sapply(1:32, function(x) paste0("T", x)),
  Year = rep(c(2000:2009), 32),
  Points_Game = rnorm(320, 100, 10)
)

# find correlation of Year and Points_Game for each team
# r - correlation coefficient
correlate <- data %>%
                group_by(Team) %>% 
                summarise(r = cor(Year, Points_Game))